1. Field of the Invention:
The present invention relates to reinforced therapeutic tubes of various types for use in the fields of anesthesia and respiratory control, etc., such as catheters, oral and nasal endotracheal tubes, tracheal cannulae, etc., and particularly pertains to reinforced therapeutic tubes with a spiral shape reinforcing material embedded into the wall of the tube body, which are excellent in kink resistance, pressure resistance and flexibility.
2. Description of the Prior Art:
Heretofore, for therapeutic tubes for bringing fluids into and out of living body, various types have been proposed. The simplest one of them all is catheter. For therapeutic tubes having more complex structures than catheters, there are available endotracheal tubes, tracheal cannulae and various tubes for drainage, etc.
Such therapeutic tubes are required to have flexibility and thin wall. However, to make the flow rate of fluid adequate by making the wall thin is quite opposite to make the tube difficult to collapse. The thinner the tube wall, the larger the hazard of the tube collapsing. Should a tube collapse and be blockaded, while in use, it would bring serious trouble or even death to the patient who is using it. For this reason, such a therapeutic tube must be of a structure which would not be blockaded, even if bent with a small radius.
Recently, proposals have been made to spirally embedded into the tube wall a reinforcing material such as stainless steel wire or piano wire, etc., being in wire form or one in thin plate form with narrow width, to provide such a therapeutic tube with resistance to blockading (Japanese Patent Application Laid-Open No. 38565/1983, etc.) Such a therapeutic tube having a spiral shape reinforcing material inside the tube wall is called "reinforced tube".
However, a tube having such a reinforcing material embedded into the tube wall in spiral form tended to expand its ID at both ends of the tube body owing to the resilience of the spiral shape reinforcing material under external force; accordingly, when the tube wall was thin, the tip of the reinforcing wire broke through and projected out of the tube wall, thereby injuring the tracheal inner wall. As a method for preventing this, it has been proposed to fix by welding the tip of the spiral wire onto a neighboring spiral wire turn, but because the wire is fine, the welding is technically difficult; even if the welding has been successfully made, strain will develop in the weld, moreover, the welded part will thickly swell up, possibly causing breakage of thin tube wall.
As an example of solving the above mentioned problem, a flat wire is spirally embedded in the tube wall. This makes for easy welding of wire, but the welded part swells up, and because of the wire being flat, flexibility is poor, thus posing problems.